Treatment of many bone disorders involves stabilizing the bone, such as by providing compression between different regions of bone thereby bringing the regions together to facilitate healing. Typically, bone screws, such as the screw device described in U.S. Pat. No. 6,001,101 to Augagneur and published application No. EP0,856,293 to Diebold et al., have utilized threaded portions having different pitches or leads to establish compression. For example, the compression effect of the Augagneur screw device arises because the travel of the distal portion is higher than the proximal portion, such that the proximal part is driven by the integral distal portion providing compression. Removal of known compression screws, however, tends to generate forces or bias generally opposing the compression achieved during insertion, which can destabilize regions of bone. Another disadvantage of known compression screws is that the threads provide insufficient surface area or purchase at large lead lengths to prevent pullout or damage to the bone.
There is a need, therefore, for an improved bone screw.